The Danger Room is a training facility built for the X-Men as part of the various incarnations of the X-Mansion.

Early Designs

The first Danger Room was filled with traps, projectile firing devices, flamethrowers, and mechanical dangers such as presses, collapsing walls and the like intended to challenge the trainee. Meanwhile, an observer is in the overhanging control booth managing the room's mechanisms to oversee the exercise while manually ensuring the subject's safety. Later the Danger Room was upgraded with machines and robots for the X-Men to fight against. The older version of the Danger Room was installed in the west coast mutant school, Academy X.

After befriending the Shi'ar the X-Men rebuilt the Danger Room with Shi'ar hard-light holographic technology. These upgrades were largely added by Dr. Hank McCoy (Beast). The Danger Room is located in the X-Mansion; every destruction of the latter led to a rebuilding, and usually upgrading, of the Danger Room. The training facility has endured extensive damage over the years, usually from X-Men training or X-Men going rogue, as Colossus did during The Muir Island Saga. Supervillains have dealt critical damage to it as well as taking over the facility, especially Arcade. The security and safety protocols that ensure the safety of anyone using the Danger Room have frequently been disrupted, tampered with by villains, failed, or have been completely negated in all the years of its use, each time happening more frequently as the room began to get more and more upgraded.

Objects in the current Danger Room are holograms surrounded by force fields. This was shown when a student (Eddie “Wing” Tancredi) managed to kill himself by jumping from a holographic cliff face.

Abilities

Able to create realistic holographic projections, enhanced strength and durability, control other machines, flight, energy blasts and detailed knowledge of the X-Men.

Gaining Self-Awareness

The Danger Room eventually developed self-awareness. This was noticed by Wolverine, who mentioned that it was 'acting twitchy all semester'. The first thing it does is convince Wing, who has recently been depowered by Ord's cure, to kill himself. The next thing it does is take control of an old, broken Sentinel robot and knock out all the psychics within the X-Mansion. During the Sentinel's attack, Cyclops orders Shadowcat and the students to go hide in the Danger Room for safety. While there they find the corpse of Wing. The Danger Room reanimates the corpse and attacks the students. Apart from Wing, there are no actual fatalities among the students. After being freed from its prison, it takes the form of a woman. She is dubbed 'Danger' and attacks the X-Men. After beating them, she travels to Genosha to kill Professor Xavier.

Xavier was revealed to have known of the Danger Room's sentience and chosen not to reveal it, much to the dismay of the X-Men. During the battle on Genosha, she takes control of Cassandra Nova's second Wild Sentinel and engages Beast in a vicious and brutal fight while the other X-Men take on the Wild Sentinel. After Beast destroys her body, "Danger's" consciousness was presumed to still exist within the conflicted consciousness of the Wild Sentinel.

Backup Model

A backup of Danger’s code was activated by one of the students at Xavier’s school under Mystique’s orders. This second Danger built itself a body. Several students were able to defeat the backup model before it had a chance to come fully online.

Ord and the Breakworld

Later, the original Danger reappears in a new humanoid form, similar to her previous one, in which she infiltrated S.W.O.R.D. headquarters to speak with Ord of the Breakworld and offer her assistance.

Danger and Ord both ended up on Breakworld, along with the X-Men and S.W.O.R.D., and after the robot encountered Emma Frost and an unconscious Cyclops, Emma told the robot that despite its supposed enmity it has let the mutants live too often, meaning it hasn't overcome its parent programming, so it cannot kill any mutant. Cyclops recovers, and Emma tells Danger to help the X-Men in Breakworld, and in exchange, it will be given Professor Xavier. Danger later attacks some of Breakworld's inhabitants and sides with the X-Men and S.W.O.R.D.

Revenge

After the Breakworld incident, S.W.O.R.D. takes Danger into custody. When the S.W.O.R.D. headquarters is destroyed during Secret Invasion, Danger escapes and goes to Australia, taking on the form of an anthropologist from Melbourne University. She approaches Rogue in her disguise but is targeted by a low flying Shi'ar salvage spacecraft, where she reveals who she really is and that she is going to use Rogue as a conduit so she can get her revenge on Professor Xavier.

After being damaged by the crew, she warps the entire area with her holographic projections of past moments within Rogue's life as well as other famous moments from the X-Men's history. Xavier confronts Danger and she reveals she intended to make Rogue absorb all his powers and memories permanently, leaving him crippled and useless. Xavier reveals that when she first said, “Where am I?”, he consulted her Shi'ar makers who assured him it was not possible she could have gained self-awareness and that he had no way of knowing what she was or would become. He tried to free her but because she was really billions of lines of machine code, he didn't know which lines to erase without lobotomizing her. Because of not knowing what she was capable of, if he had freed her, she might have killed his X-Men because she had the knowledge and power, so instead he did nothing and watched her suffer. Xavier ends her suffering by repairing her. She then sides with Xavier, Rogue and Gambit and takes out the Shi'ar salvage crew. Afterwards, with Xavier she helps Rogue gain full control over her powers.

"Future Danger"

In a future timeline, Victorious is able to take control of Danger. Danger uses her knowledge of the X-Men to kill the entire team. This allows Victorious to face and defeat the Avengers and then take control of the world. His plan is defeated when a future version of Billy (one of the Travelers) brings a group of seniors from Xavier's school into the future to fight Danger before she faces the X-Men. These seniors never trained in the Danger Room and therefore Danger is not equipped to defeat them. Danger takes the form of the X-Men to fight the seniors but is defeated. The X-Men, now safe from Danger, team up with the Avengers to defeat Victorious.

Powers and Abilities

As Danger gained self-awareness and adopted a more humanoid appearance, she has shown enhanced strength and durability, project hard-light holographic projections that can affect entire areas, energy blasts, flight, the ability to rebuild herself after her body is destroyed (at one point even rebuilding herself with butterfly-like wings which are soon destroyed by Beast) and control over other machines. She is able to bring other machines into self-awareness and upload herself into other machines to build and operate new bodies. She also possesses more detailed knowledge of the X-Men and their combat skills than any other source, having trained against them as the Danger Room.